Some publisher’s print books and e-books were recently pulled from Amazon.com’s virtual shelves over a pricing dispute. Publishers have objected to Amazon’s $9.99 pricing saying that it is too low and could hurt hardcover book sales.

To preserve the more lucrative hardcover business, some publishers will now impose delays on the release of digital copies.

Amazon isn’t disclosing much about their strategy and it is widely speculated that they are guarding against market share challenges from Barnes & Noble’s Nook, Sony Corp‘s e-book readers and more importantly, the long-awaited Apple iPad tablet computer with a new online book store modeled on iTunes. It is rumored that some publishers may offer e-titles to Apple before they are allowed to go on sale at Amazon.com.

To offset the effects of reduced inventory, Amazon has been offering a new 70% royalty option for authors and publishers who want to release e-books through its online store for use on Kindle.

The protectionist move by publishers coupled with Amazon’s insistence on lowering e-Book prices while raising royalty rates has the potential to radically change the balance of power in the e-book publishing industry.